Digital watermarking is an efficient technology to hide information in digital content such as images and video. In a general watermarking system, a message is converted to a watermark using a watermark generator. The watermark may be embedded in digital content using a watermark encoder. The watermarked content is transmitted through a channel, such as the Internet, to consumers. Distortions such as transcoding, filtering and resolution change may be introduced to the watermarked content during the transmission. A watermark decoder may be used to attempt to detect the watermark in the distorted watermarked content and thereby retrieve the message.
Common distortions include transcoding, frame rate changes, camcorder capture, and geometric distortions such as cropping, rotation, shifting, and scaling. Geometric distortions often fail watermark decoding in many watermarking algorithms by destroying synchronization between the watermark encoder and the watermark decoder. Synchronization in some watermarking algorithms may refer to aligning a block at the watermark decoder with the corresponding block at the watermark encoder. Geometric distortions often destroy the alignment.
The subject matter claimed herein is not limited to embodiments that solve any disadvantages or that operate only in environments such as those described above. Rather, this background is only provided to illustrate one exemplary technology area where some embodiments described herein may be practiced.